1. Field of the Invention
The present invention relates to a pet litter box comprised of relatively light weight, easily cleaned components which inter fit to internally entrap odors from unabsorbed liquid waste, and which are characterized by sufficient structural rigidity to support the weight of a pet.
2. Description Of The Prior Art
Many household pets are trained to use pet litter boxes containing a commercial litter material that can be pawed by the pet to cover solid waste material. The litter also absorbs liquid waste material up to its absorbent capacity, beyond which point the litter has to be replaced to prevent odor problems.
The useful service life of the litter can be extended by providing openings in the litter support tray and allowing localized unabsorbed liquid waste material to pass through the tray into a lower pan for periodic emptying.
Some prior litter box designs, such as that disclosed in U.S. Pat. Nos. 3,476,083 and 4,696,257, aerate the liquid waste material in the collecting pan. The litter box of the '083 patent accomplishes this by providing a pan larger than the structure it supports so that openings to atmosphere are formed between them. The '257 structure is aerated by providing holes in the sides of the collecting pan. Such aeration was apparently considered to be desirable to reduce the volume of collected liquid waste material, but this also presents the problem of undesirable odors.
The litter box of U.S. Pat. No. 4,771,731 does not provide for aeration, closely nesting the upper and lower pans to isolate the odor of the liquid waste that collects in the lower pan. However, it requires placement in the lower pan of a relatively expensive disposable deodorant containing bag. The disclosure thus teaches away from the use of a lower pan that can collect waste for periodic emptying, instead depending upon the use of a bag that itself has to be periodically replaced along with the litter.
U.S. Pat. No. 2,971,493 discloses an arrangement of upper and lower pans similar to that of the '731 patent, but screening is used in the upper pan to bear the weight of the litter and the pet. Screening is specified in order to catch the claws of the pet and discourage energetic pawing and scattering of litter. However, screening is not structurally rigid and tends to bow under any significant weight. To keep the litter on the bowed screen out of contact with the collected liquid waste below would require that the height of the liquid waste compartment be increased. This would undesirably increase the overall height of the litter box and thereby increase its tendency to tip over.